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I was just browsing medical studies for info about creatine and hypertension (since my BP is up since I've been eating all the creatine in the world), and I stumbled across this:
Their study suggests creatine supplementation might raise homocysteine levels. High levels of homocysteine are strongly associated with cardiovascular disease and has other very nasty effects as well. I thought this was noteworthy enough to post.
The Effect of L-Arginine and Creatine on Vascular Function and Homocysteine Metabolism
Background
Studies with L-arginine supplementation have shown inconsistent effects on endothelial function. The generation of guanidinoacetate (GAA) from L-arginine with subsequent formation of creatine and homocysteine and consumption of methionine may reduce the pool of L-arginine available for nitric oxide generation. Experimental studies suggest that creatine supplementation might block this pathway. We sought to determine the effects of L-arginine, creatine, or the combination on endothelium-dependent vasodilation and homocysteine metabolism in patients with coronary artery disease.
Methods
Patients with coronary artery disease were randomized to L-arginine (9gm/day), creatine (21gm/day), L-arginine plus creatine, or placebo for 4 days (n=26–29/group). Brachial artery flow-mediated dilation and plasma levels of L-arginine, creatine, homocysteine, methionine, and GAA were measured at baseline and follow up.
Results
L-arginine and creatine supplementation had no effects on vascular function. L-arginine alone increased GAA (P<0.01) and the ratio of homocysteine to methionine (P<0.01) suggesting increased methylation demand. The combination of creatinine and L-arginine did not suppress GAA production or prevent the increase in homocysteine-to-methionine ratio. Unexpectedly, creatine supplementation (alone or in combination with L-arginine) was associated with an 11 to 20% increase in homocysteine concentration (P<0.05), which was not attributable to worsened renal function, providing evidence against an effect of creatine on decreasing methylation demand.
Conclusion
The present study provides no evidence that L-arginine supplementation improves endothelial function and suggests that L-arginine may increase methylation demand. Creatine supplementation failed to alter the actions of L-arginine on vascular function or suppress methylation demand. The unexpected increase in homocysteine levels following creatine supplementation could have adverse effects and merits further study, since creatine is a commonly used dietary supplement.
Background
Studies with L-arginine supplementation have shown inconsistent effects on endothelial function. The generation of guanidinoacetate (GAA) from L-arginine with subsequent formation of creatine and homocysteine and consumption of methionine may reduce the pool of L-arginine available for nitric oxide generation. Experimental studies suggest that creatine supplementation might block this pathway. We sought to determine the effects of L-arginine, creatine, or the combination on endothelium-dependent vasodilation and homocysteine metabolism in patients with coronary artery disease.
Methods
Patients with coronary artery disease were randomized to L-arginine (9gm/day), creatine (21gm/day), L-arginine plus creatine, or placebo for 4 days (n=26–29/group). Brachial artery flow-mediated dilation and plasma levels of L-arginine, creatine, homocysteine, methionine, and GAA were measured at baseline and follow up.
Results
L-arginine and creatine supplementation had no effects on vascular function. L-arginine alone increased GAA (P<0.01) and the ratio of homocysteine to methionine (P<0.01) suggesting increased methylation demand. The combination of creatinine and L-arginine did not suppress GAA production or prevent the increase in homocysteine-to-methionine ratio. Unexpectedly, creatine supplementation (alone or in combination with L-arginine) was associated with an 11 to 20% increase in homocysteine concentration (P<0.05), which was not attributable to worsened renal function, providing evidence against an effect of creatine on decreasing methylation demand.
Conclusion
The present study provides no evidence that L-arginine supplementation improves endothelial function and suggests that L-arginine may increase methylation demand. Creatine supplementation failed to alter the actions of L-arginine on vascular function or suppress methylation demand. The unexpected increase in homocysteine levels following creatine supplementation could have adverse effects and merits further study, since creatine is a commonly used dietary supplement.
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